DOC: Fix formatting of a code example
DOC: Fix formatting of a code example

One of the code examples in the docstring of
`numpy.random.Generator.multivariate_normal()` was not being displayed
properly in the built documentation.

endolith/numpy,pdebuyl/numpy,mhvk/numpy,pdebuyl/numpy,mhvk/numpy,mattip/numpy,numpy/numpy,anntzer/numpy,mhvk/numpy,seberg/numpy,charris/numpy,jakirkham/numpy,numpy/numpy,seberg/numpy,pdebuyl/numpy,jakirkham/numpy,seberg/numpy,anntzer/numpy,anntzer/numpy,rgommers/numpy,rgommers/numpy,charris/numpy,jakirkham/numpy,jakirkham/numpy,rgommers/numpy,jakirkham/numpy,rgommers/numpy,seberg/numpy,mhvk/numpy,anntzer/numpy,endolith/numpy,mhvk/numpy,charris/numpy,endolith/numpy,charris/numpy,endolith/numpy,numpy/numpy,pdebuyl/numpy,mattip/numpy,mattip/numpy,mattip/numpy,numpy/numpy